First tornadoes in 18 years hit Sioux Falls, leaving destruction in their wake

PHOTO: Sioux Falls residents begin the recovery process after a devastating tornado, in South Dakota, Sept. 11, 2019.PlayArgus Leader via USA Today Network
WATCH Tornado outbreak across the Midwest

Powerful tornadoes left a trail of destruction in Sioux Falls, South Dakota, toppling trees, knocking out power to thousands and seriously damaging both area hospitals.

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No deaths or serious injuries were reported after the overnight twisters, Sioux Falls Mayor Paul TenHaken said Wednesday. Thirty-seven structures collapsed or have major integrity issues, officials said.

The three EF-2 tornadoes confirmed to have touched down in Sioux Falls are the first there since June 2001.

PHOTO: The Avera dome shows damage after a devastating tornado hit in Sioux Falls, S.D., Sept. 11, 2019. Argus Leader via USA Today Network
The Avera dome shows damage after a devastating tornado hit in Sioux Falls, S.D., Sept. 11, 2019.
PHOTO: A living room is pictured after a devastating tornado hit in Sioux Falls, Sept. 11, 2019. Argus Leader via USA Today Network
A living room is pictured after a devastating tornado hit in Sioux Falls, Sept. 11, 2019.
PHOTO: Whitnee Fester puts up caution tape outside of the Avera dome after a devastating tornado hit in Sioux Falls, S.D., Sept. 11, 2019. Argus Leader via USA Today Network
Whitnee Fester puts up caution tape outside of the Avera dome after a devastating tornado hit in Sioux Falls, S.D., Sept. 11, 2019.

The Avera Behavioral Health Hospital, one of those damaged, said all patients were safe and some were moved to other facilities, according to a hospital spokesperson. Several people there suffered minor injuries from the roof collapsing, said the hospital's president and CEO, David Flicek.

PHOTO: A tornado ripped off part of the Avera Behavioral Health Hospitals roof and caused significant damage to the buildings windows, overnight Sept. 11, 2019, in Sioux Falls, S.D. KSFY
A tornado ripped off part of the Avera Behavioral Health Hospital's roof and caused significant damage to the building's windows, overnight Sept. 11, 2019, in Sioux Falls, S.D.

With so much debris on the roads, a "No Travel Advisory" was issued in the city. The advisory was lifted at 8 a.m. Wednesday, but police urged drivers to use caution "as there may be areas still impacted, unreported downed power lines, tree debris or other road hazards."

PHOTO: Crews work on repairing a gas leak at Western Ave. and 33rd St. after a late night Tuesday storm in Sioux Falls, Sept. 11, 2019.
Sioux Falls Argus Leader via USA Today Network
Crews work on repairing a gas leak at Western Ave. and 33rd St. after a late night Tuesday storm in Sioux Falls, Sept. 11, 2019.

Four tornadoes were reported in South Dakota -- three of which have been confirmed -- and seven were reported in Wyoming as severe weather struck the region Tuesday night.

PHOTO: Damage in the aftermath of storm is seen in Sioux Falls, S.D., Sept. 11, 2019. Derek Thompson/Derekjt.com via Reuters
Damage in the aftermath of storm is seen in Sioux Falls, S.D., Sept. 11, 2019.

"It was really a crazy night," Sioux Falls resident Charles Roskowiak told ABC News. "There was an alert on [my] phone -- there was a tornado warning in the area."

"We heard this massive explosion," he added. "There's just pounding rain and we see this tree, this massive tree, sitting on top of our house. ... I'm surprised the house didn't go down."

The tornado warnings began at 11 p.m. CDT, officials said. Only some of the sirens in town were activated, which the mayor attributed to human error.

PHOTO: An auto parts store damaged during the storm is seen in Sioux Falls, S.D., Sept. 11, 2019. Derek Thompson/Derekjt.com via Reuters
An auto parts store damaged during the storm is seen in Sioux Falls, S.D., Sept. 11, 2019.
PHOTO: Debris from a violent storm litters a residential area of Sioux Falls, S.D., Sept. 11, 2019. Sioux Falls Argus Leader via USA Today Network
Debris from a violent storm litters a residential area of Sioux Falls, S.D., Sept. 11, 2019.

And the threat is not over. On Wednesday night, severe thunderstorms are possible from Wyoming to Michigan -- including, again, Sioux Falls.

The main threats will be strong wind gusts and large hail. A few tornadoes are also possible, particularly in western Nebraska.

Stronger, slow-moving thunderstorms can bring torrential rain and trigger flash flooding. Flash flood watches are in effect from Nebraska to Sioux Falls to southwestern Minnesota.

ABC News' Alex Perez, Will Gretsky and Ahmad Hemingway contributed to this report.